1. Field of the Invention
This invention relates to a tensioner for an endless power transmission belt or the like, an improved part for such a tensioner or the like as well as to methods of making such a tensioner and improved part.
2. Prior Art Statement
It is known in the art to provide a tensioner for a power transmission belt that is adapted to be operated in an endless path, the tensioner comprising a support means for being fixed relative to the belt, a belt engaging means carried by the support means and being movable relative thereto, force producing means operatively associated with the support means and the belt engaging means for urging the belt engaging means relative to the support means in a belt tensioning direction and against the belt with a force to tension the belt, and a fluid operated transmitting means operatively associated with the force producing means and the belt engaging means for translating forces therebetween whereby the force producing means is adapted to be disposed remote from the belt engaging means, the fluid operated transmitting means including a piston and cylinder means having a cylinder member and a piston member disposed in the cylinder member with one of the members being adapted to be fixed to define part of the support means with the other of the members being movable relative thereto and being operatively associated with the belt engaging means.
Examples of tensioners of the above-mentioned type are provided in the following co-pending patent application of one of the applicants of this invention and two U.S patents:
(1) U.S patent application, Ser. No. 296,693, filed Aug. 27, 1981, of Leslie B. Wilson one of the applicants of this application. PA1 (2) U.S. Pat. No. 4,051,742--Johansson PA1 (3) U.S. Pat. No. 4,094,205--Cook. PA1 (4) U.S. Pat. No. 3,168,278--Ogden.
It appears from item (1) above that the force producing means comprises a mechanical spring unit which has the force thereof transmitted to a piston member that is interconnected to an idler pulley by a passage defining means of a fluid transmitting means, the passage defining means having a flow control valve therein to be more restrictive to the flow of fluid therethrough from the belt engaging means to the spring unit than from the spring unit to the belt engaging means for a dampening purpose.
It appears from item (2) above that a sensing unit senses slack in a belt and directs fluid pressure to a piston and cylinder unit that moves a belt engaging means in a belt tensioning direction with an increasing force, the piston and cylinder means appearing to be truly cylindrical in shape.
It appears from item (3) above that a piston and cylinder unit is utilized to tension a belt and has increasing pressure directed thereto as increased torque is provided by the belt, the piston and cylinder unit appearing to be truly cylindrical in shape.
It is also known in the art to provide a fluid operated piston and cylinder device comprising a cylinder member provided with a chamber therein, a piston member disposed in the chamber whereby one of the members is adapted to be fixed with the other of the members being movable relative thereto, the chamber of said cylinder member defining an internal peripheral side wall of the cylinder member, and a rolling diaphragm carried by the cylinder member for rolling against the peripheral side wall, the piston member being operatively associated with the rolling diaphragm.
Such a device can have the piston member contoured, the cylinder member contoured or both the piston member and the cylinder member contoured as set forth in the following U.S. patent: